Strategy:
Mormo doesn't start out too great. Low accuracy, damage, dodge, health... basically every stat. However, when he promotes and gains some new neat Epics, you'll see him start to become much better. He's the only Kraken Skulls companion that can learn Relentless/Burst Fire/Mojo Echo, and he's right up there as one of the best!

He can either be a single target hitting Witchdoctor or an AoE one. The AoE method seems like a better build, as the common purpose of Witchdoctors are to hit multiple enemies - otherwise, you'd just use a Musketeer, right? If you want him to be a single hitter, give him Jobu's Ruse and Mojo Echo 2. For the AoE build, train either Mojo Echo and Improved Mojo Blast 2 or Mojo Echo, Jobu's Ruse, and Improved Mojo Blast. While Mojo Echo 2 is great, considering that Witchdoctors will miss more than any other class, you may see a fizzle happening occasionally, which will result in the Mojo Echo chain ending. It is a great Epic, but with the limited number of trainable ones, it may be ideal to avoid it for now. When he promotes again, however...

Pro Tip: Did you know that El Toro is the only companion with increased movement? Use Mormo's Vulture's Gift on him, and you'll see him flying across the battleboard with ease!